In nowadays, the silica-titania hybrid film is widely applied in the optics field and usually acts as, for example, a high refractive index film, an optical waveguide component, an nonlinear optical material and various different kinds of optical protective layers. The conventional methods for manufacturing various silica-titania films include an evaporation scheme, a sputtering scheme, a chemical vapor deposition (CVD) scheme, a plasma enhanced chemical vapor deposition (PECVD) scheme, an atomic layer deposition (ALD) scheme and the like.
No matter which kind method is selected to manufacture the above-mentioned hybrid film, the uniformity issue of mixed silicon dioxide (SiO2) and titanium dioxide (TiO2) molecules and the issue how to ensure a good interfacial adhesion between the molecules will happen. Moreover, the vacuum systems are required of the embodiments of above mentioned methods which the processing equipment cost is relatively high, and the large-scale production is difficult. Furthermore, the coating ability of the vapor deposition or sputtering on a porous substrate is poor, and the disadvantages of chemical vapor deposition are high reaction temperatures and it will possibly damage the substrates.
For the aforementioned reasons, the synthetic ways to manufacture the hybrid films were gradually developed. One of it is to take advantage of a sol-gel reaction process and in conjunction with the appropriate organic molecular materials as the interfacial adhesion between the colloidal particles to prepare organic/inorganic polymer hybrid materials. The advantages of Sol-gel method are high purity, good chemical uniformity, easy to control the constituent ratio, able to be coated on large and complex substrate, the process is simple and the process temperature is low, the production dimensions is large, low manufacturing costs and cheap equipment that various aspects of advantages are applied to overcome present issues in conventional technology.
FIG. 1(a) to FIG. 1(c) show schematic diagrams respectively illustrating various mixing types regarding silica molecules and titania molecules in the silica/titania hybrid film in the prior art; FIG. 1(a) shows a mixed state that there is none of chemical bonds existing between SiO2 molecules 10 and TiO2 molecules 12 and the SiO2 molecules 10 and TiO2 molecules 12 exist in the film in a mixture state; FIG. 1(b) shows that SiO2 molecules 10 and TiO2 molecules 12 are bonded with each other through chemical bonds; and FIG. 1(c) shows that SiO2 molecules 10 and TiO2 molecules 12 are bonded with each other through the organic molecules 14 acting as interface adhesive substance.
However, whether it is a mixture of FIG. 1(a), the chemical bonding of FIG. 1(b) or the interfacial adhesion mixing state of FIG. 1(c), the colloidal particles cannot be stacked tightly issues are existing. The film surface is not fine-scale morphology under microscopic view, and the obvious defects of non-uniform structure and different chemical constitutions of the film need to be further improved.
There is a need to solve the above deficiencies/issues.